Echinacea, commonly known as coneflower, is a member of the Asteraceae family. According to the most widely accepted taxonomic treatment, the genus Echinacea is composed of eleven taxa, nine North American indigenous species and two varieties [See McGregor, R. L., Univ. Of Kansas Science Bulletin 48(4):113-142 (1968).] This article and all publications cited in this application are herein incorporated by reference.
Echinacea has a rich tradition of medicinal use by North American Plains Indians. Currently, three of the species, E. angustifolia, E. pallida, and E. purpurea, have commercial value as herbal remedies for general immune-boosting effects. These species along with E. paradoxa and E. tennesseensis are also of ornamental value and grown as popular landscape plants and cut flowers.
Echinacea are herbaceous perennial plants having basal rosette of leaves and erect flowering stems. The flower heads have many fertile disc florets borne on a flattened to raised receptacle, and typically have a single outer whorl of sterile ray florets. The flower heads have a bristly appearance due to the stiff, sharp palea subtending the disc florets. As a garden perennial, E. purpurea is most common, and has flower colors restricted to purple through pink shades to white. Hybridization with yellow flowered E. paradoxa has broadened the color range [See Rice, G., Plantsman 212-219 (2007).]
Echinacea can be propagated from seed, cuttings, divisions, and through tissue culture. Seed germination protocols for several of the species are now well known in the art [See Ault, J. R., Coneflower, Echinacea species, p. 799-822. In: Flower Breeding and Genetics: Issues, Challenges, and Opportunities for the 21st Century, Anderson, N. O., ed., The Netherlands, Springer, (2006).]
Hybridization studies revealed that Echinacea species hybridize easily and many fertile F1 hybrids can be produced. Echinacea breeding has barriers. Historically, the genus was described as being completely self-incompatible. A later study of E. angustifolia reported up to 9% self-pollinations. While the degree and type of self-incompatibility remains unknown, breeding strategies employing mass selection or phenotypic recurrent selection offer models for the development and maintenance of Echinacea seed lines [See Ault, J. R., Coneflower, Echinacea species, p. 799-822. In: Flower Breeding and Genetics: Issues, Challenges, and Opportunities for the 21st Century, Anderson, N. O., ed., The Netherlands, Springer, (2006).]
With any successful breeding program, there are numerous steps in the development of novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. For the horticultural industry, these important traits can include novel colors, resistance to diseases and insects, tolerance to drought and heat, or superior garden performance.
Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of cultivar used commercially (e.g., F1 hybrid cultivar, pureline cultivar, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Backcross breeding is used to transfer one or a few favorable genes for a highly heritable trait into a desirable cultivar. This approach has been used extensively for breeding disease-resistant cultivars. Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Each breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful cultivars produced per unit of input (e.g., per year, per dollar expended, etc.).
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial cultivars; those still deficient in a few traits can be used as parents to produce new populations for further selection.
These processes, which lead to the final step of marketing and distribution, require several from the time the first cross is made. Therefore, development of new cultivars is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard cultivar. If a single observation is inconclusive, replicated observations provide a better estimate of its genetic worth.
Mass and recurrent selections can be used to improve populations of either self- or cross-pollinating crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
Backcross breeding has been used to transfer genes for a simply inherited, highly heritable trait into a desirable homozygous cultivar or inbred line which is the recurrent parent. The source of the trait to be transferred is called the donor parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent. After the initial cross, individuals possessing the phenotype of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., cultivar) and the desirable trait transferred from the donor parent.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.